Fuel injection nozzle

ABSTRACT

A FUEL INJECTION NOZZLE INCLUDING A TURBULENCE CHAMBER FROM WHICH ONE PART OF THE FUEL ADMITTED TO THE NOZZLE IS INJECTED INTO A COMBUSTION ZONE THROUGH A NOZZLE OPENING, WHILE THE OTHER PART OF THE FUEL IS RETURNED FROM THE TURBULENCE CHAMBER TO A FUEL TANK THROUGH A RETURN CHANNEL PROVIDED IN THE NOZZLE AND CONTROLLED BY A DISC VALVE, THE VALVE PLATE OF SAID DISC VALVE IS URGED INTO A CLOSED POSITION BY AN ADJUSTABLE CLOSING SPRING ENGAGING THE VALVE PLATE ECCENTRICALLY, SAID VALVE PLATE IS URGED INTO AN OPEN POSITION BY THE PRESSURE PREVAILING IN SAID TUBULENCE CHAMBER. WHEN SAID PRESSURE OVERCOMES THE FORCES OF SAID SPRING, THE VALVE PLATE IS UNSEATED BY A TILTING MOTION MADE POSSIBLE BY SAID OFFCENTER ENGAGEMENT.

United States Patent Inventors Paul Fussner Sindelfingen; Gunter Hirsch, Kornwostheim; Dieter Vogt, Stuttgart-Weilimdori, Germany Appl. No. 866,244 Filed Oct. 14, 1969 Patented June 28, 1971 Assignee Robert Bosch GmbH Stuttgart, Germany Priority Nov. 2, 1968 Germany P 18 06 674.5

FUEL INJECTION NOZZLE 9 Claims, 1 Drawing Fig.

0.8. CI 239/533, 239/124, 239/126, 239/577 Int. Cl 1305b 1/30, BOSb 9/00 Field of Search 239/124, 5 3 3 5 7 7 Primary ExaminerM. Henson Wood, Jr. Assistant Examiner-Reinhold W. Thieme Attorney-Edwin E. Greigg ABSTRACT: A fuel injection nozzle including a turbulence chamber from which one part of the fuel admitted to the nozzle is injected into a combustion zone through a nozzle opening, while the other part of the fuel is returned from the turbulence chamber to a fuel tank through a return channel provided in the nonle and controlled by a disc valve; the valve plate of said disc valve is urged into a closed position by an adjustable closing spring engaging the valve plate eccentrically, said valve plate is urged into an open position by the pressure prevailing in said turbulence chamber. When said pressure overcomes the force of said spring, the valve plate is unseated by a tilting motion made possible by said offcenter engagement.

1 FUEL INJECTION NOZZLE BACKGROUND OF THE INVENTION This invention relates to a fuel injection nozzle wherein the injected fuel quantities are changed by varying the bypassing fuel quantities taken out from the fuel flow introduced into the I nozzle and wherein the nozzle is provided with a turbulence chamber in which the fuel supply channels merge tangentially and with-which a return channel communicates. In the latter there is disposed a closing element which is opened by the pressure prevailing in the turbulence chamber, overcoming the force of a closing spring which may be adjusted for varying the fuel quantities.

Fuel injection nozzles of this type (such as, for example, disclosed in German Pat. No. 1,138,987) find application in particular in oil burning apparatus using heating oil as fuel which is delivered by a pump under constant pressure to the injection nozzle. The latter injects one part of the fuel into the combustion zone and returns the other part through a return conduit to the fuel tank or to the suction side of said pump. The quantities to be injected are determined by the pressure prevailing in the turbulence chamber.

When the desired heat output is attained, the supply of heating oil to the injection nozzle is interrupted by the stoppage of the pump and the aforenoted closing element, under the effect of the closing spring, shuts off the return channel. As soon as heating oil is again supplied, the closing element reopens which, because of the sudden flow of the heating oil, occurs in an impactlike manner. The closing element is thus displaced against the force of the closing spring and thereafter assumes a position in which it provides a certain flow passage section determined by the equilibrium of a force exerted to a face of the closing element by the fuel pressure in the opening direction and the force of the closing spring exerted in the closing direction. The said flow passage section determines the fuel injection control pressure in the turbulence chamber.

In fuel injection nozzles of the aforeoutlined type, the most often used known closing elements (such as, for example, the one disclosed in the periodical Interavia 1952, page 398, FIG. E) have the disadvantage that they do not operate entirely in a frictionless manner; consequently, due to the starting impacts mentioned hereinbefore, the closing element opens to an excessive extent and then often is not able to positively assume a position of equilibrium. As a result, disadvantageous fluctuations of the injected quantities per time unit occur.

OBJECT AND SUMMARY OF THE INVENTION It is the principal object of the invention to provide an improved fuel injection nozzle from which the aforeoutlined disadvantages are eliminated.

Briefly stated, according to the invention, the closing element is formed as a disc valve, the valve plate of which is loaded offcenter by the closing spring. Thus, for the opening of the return channel, the valve plate is tilted about an edge portion thereof. The force of the closing spring may be varied by an adjusting means threadedly disposed in the return channel.

The invention will be better understood, as well as further objects and advantages will become more apparent, from the ensuing detailed specification of a preferred, although exemplary, embodiment of-the invention taken in conjunction with the sole FIGURE showing the embodiment in axial section.

DESCRIPTION OF THE EMBODIMENT In a hollow nozzle body 1, a sleeve bolt 2 threadedly received in a bore 1', clamps an insert 3 against an inner wall portion of nozzle body 1. Between the insert 3 and the nozzle body 1 there is disposed a turbulence chamber generally indicated at 4 which is formed of a cylindrical cavity 3' provided in the terminal face of insert 3 and an adjoining conical space 1" defined by wallportions of nozzle body I. The conical space 1" continues in a nozzle opening 5. The cylindrical cavity 3' of the turbulence chamber 4 communicates through an axial bore 6 of the insert 3 with a fuel return channel formed of the inner bore 7 of sleeve bolt 2. A plurality of fuelsupply channels 8 (only one is shown) merge tangentially into the turbulence chamber 4.

The insert 3 has a sleevelike portion 3" received in a fluidtight manner by the terminal portion of the bore 7 of the sleeve bolt 2. The frontal face of sleeve portion 3" within bore.

7 serves as a valve seat forming part of a disc valve. The latter includes a valve plate 10 which is urged against said valve seat by a closing spring 11 supported at its end remote from the valve seat by a spring seat disc 12, which, in turn, is held by asetting screw 13 threadedly received in bore 7. It is seen that by turning the setting screw l3, the force of coil spring 11 may be varied.

The spring 11 engages the valve plate 10 offcenter which is achieved by providing the valve plate 10 with a guiding or support lug 14 secured eccentrically thereto and adapted to be surrounded by the spring 11. Further, the maximum diameter of the valve plate 10 is only slightly smaller than that of bore 7. By virtue of these last-named two features, a force exerted on the underside (or base) of valve plate 10 and sufficient to overcome the force of closing spring 11, causes a tilting unseating of valve plate 10 about the edge thereof, while a radial displacement of the valve plate 10 on the valve seat is prevented.

Since the spring seat disc 12 is centrally held on the adjusting means 13, while the spring 11 loads the valve plate 10 in eccentric manner, the axis of the coil spring 11 and that of the adjusting means 13 (or insert 3) defines an angle which varies dependent upon the extent the spring 11 is compressed. In order to ensure that the spring seat disc is guided centrally by the setting screw 13, the latter terminates in a cone 15, the apical portion of which nests in a conical depression 16 having a wider angle than that of cone 15. Such a difference in the cone angles is necessary to prevent there the appearance of forces which would exert a bending moment on the spring 11.

The valve plate 10 has the shape of a truncated cone of small height; its base (i.e. its frontal face of larger diameter) is adjacent the insert 3. In order to ensure that the valve plate 10 engages the valve seat only with a narrow annular marginal portion of said base, the bore 6 is enlarged into a circular depression 17, the diameter of which is only very slightly smaller than the largest diameter of the valve plate 10. A narrow fluidtight seat of this structure has the advantage that the specific sealing forces are relatively large, resulting in a good fluidtight seal. Also, the narrow valve seat face is automatically cleaned by the throughflowing fuel. In addition, almost the entire lower face of the valve plate 10 is affected by the fuel; consequently, the difference between the opening forces exerted on the closing element before and after the unseating of a valve plate 10 is small. Stated differently, as long as the valve plate 10 is seated (i.e. the closing element is closed), the valve plate surface acted upon by the opening pressure is that part of the valve plate base which lies inside the contour of the circular depression 17. After the unseating of valve plate 10, on the other hand, the only slightly larger entire base is exposed to the opening pressure.

The external face of the nozzle-body l is provided with a thread 19 by means of which the nozzle body may be screwed into a threaded tubular nozzle holder (not shown). The nozzle holder then communicates with a pressure conduit, also not shown, leading from a delivery pump.

. OPERATION OF THE EMBODIMENT flows across the bore 6 into the depression ll7 under the valve plate 10. As soon as a sufficiently high pressure is built up in the turbulence chamber 4, the valve plate 10 tilts about its edge overcoming the force of the spring 1 1, so that part of the heating oil may flow into the return channel 7. In order to ensure a throttle-free passage of the fuel, into the setting screw 13 there are milled axial channels 23. By turning the setting screw 13 with respect to sleeve bolt 2, the axial position of the former in the latter may be changed thus varying the preload of spring 11, that is, varying the pressure required for the opening of the closing element. This externally adjustable opening pressure determines the pressure prevailing in the turbulence chamber 4; the last-named pressure, in turn, determines the quantities to be injected through nozzle opening 5 into the firing zone.

We claim:

1. In a fuel injection nozzle of the known type that includes (A) a turbulence chamber, (B) supply conduit means merging into said turbulence chamber and delivering fuel under pressure thereto, (C) a nozzle opening in communication with said turbulence chamber, (D) a return channel in communication with said turbulence chamber, (E) a closing element disposed in said return channel and openable by the pressure prevailing in said turbulence chamber and (F) an adjustable closing spring disposed adjacent said closing element and urging the latter into a closed position against the force of said pressure, the improvement comprising, a disc valve constituting said closing element and having a valve plate provided with an edge, said closing spring engaging said valve plate offcenter to cause a tilting opening movement of said valve plate about a portion of said edge in response to the pressure prevailing in said turbulence chamber.

2. An improvement as defined in claim 1, including an adjusting means threadedly engaged in said return channel and, when rotated, adapted to vary the force of said closing spring.

3. An improvement as defined in claim 2, wherein said turbulence chamber includes a cylindrical portion disposed remote from said noule opening, said fuel injection nozzle includes an axial bore constituting said return channel; said valve plate, said closing spring and said adjusting means are disposed in said bore.

4. An improvement as defined in claim 3, including:

A. a hollow nozzle body;

B. a sleeve bolt threadedly engaged in said nozzle body and containing said bore, outer wall portions of said sleeve bolt and inner wall portions of said nozzle body together define annular chamber means forming part of said supply conduit means; said turbulence chamber is arranged in said sleeve bolt; and

C. a valve seat cooperating with said valve plate and contained by said sleeve bolt.

5. An improvement as defined in claim 3, including:

A. a hollow sleeve body;

B. a sleeve bolt threadedly engaged in said nozzle body and containing said bore, outer wall portions of said sleeve bolt and inner wall portions of said nozzle body together define annular chamber means fonning part of said supply conduit means; said valve plate, said closing spring and said adjusting means are disposed in, and guided by said bore;

C. an axially hollow insert clamped against inner wall portions of said nozzle body by said sleeve bolt and containing at least one part of said turbulent chamber; and

D. a valve seat cooperating with said valve plate and contained by said insert.

6. An improvement as defined in claim 1, including an axial bore constituting said return channel and containing said valve plate and said closing spring; said valve plate is in the shape of a truncated cone tapering towards said closing spring, the largest diameter of said truncated cone is only slightly smaller than'the diameter of said bore.

7. An improvement as defined in claim 1, including a valve seat cooperating with said valve plate, said valve seat has an opening which communicates with said turbulence chamber and has a diameter only slightly smaller than that face of the valve plate which cooperates with said valve seat.

8. An improvement as defined in claim 2, including a spring seat disc disposed between said adjusting means and said closing spring, said adjusting means terminates in a cone, the apex of which engages said spring seat disc.

9. An improvement as defined in claim 8, wherein said spring seat disc includes a conical depression in which the apical portion of said cone nests, the angle of said conical depression is larger than that of said cone. 

